Abnormal features of oceanographic characteristics in upwelling Vietnam waters under impact of El Niño events


  • Tong Phuoc Hoang Son* Institute of Oceanography, Vietnam Academy of Science and Technology
  • Tran Van Chung Institute of Oceanography, Vietnam Academy of Science and Technology
  • Nguye Huu Huan Institute of Oceanography, Vietnam Academy of Science and Technology
  • Ngo Manh Tien Institute of Oceanography, Vietnam Academy of Science and Technology
  • Vu Van Tac Institute of Oceanography, Vietnam Academy of Science and Technology
  • Nguyen Hoang Thai Khang Institute of Oceanography, Vietnam Academy of Science and Technology
  • Nguyen Truong Thanh Hoi Institute of Oceanography, Vietnam Academy of Science and Technology
  • Marine Herrmann LEGOS, IRD-CNES-CNRS-Université de Toulouse, University of Sciences and Technology of Hanoi, Vietnam Academy of Science and Technology
  • Eko Siswanto Japan Agency for Marine-Earth Science and Technology (JAMSTEC)




Weakening of Vietnam waters Upwelling, ENSO, El Nino decline phase, oceanographic characteristics anomalies


The summer upwelling that occurs in coastal waters of South Central Vietnam is one of the major hydrographic features in the South China Sea. A weakening of the upwelling after major El Niño events was observed in the literature for previous El Nino events and was verified here from the analysis of new satellite image data sets of sea surface temperature (SST) and surface wind. The analysis of empirical orthogonal function (EOF) from of monthly SST as well as of temporal and spatial variations of SST and wind force allow us to identify abnormal characteristics in ocean surface water that happened after El Niño episode, in agreement with previous studies. Those abnormal characteristics in Vietnam upwelling waters appeared mainly during the summers of 1998, 2003, 2010 and 2016 years for the El Niño decline phase. The upwelling weakening during El Niño decline episodes is associated with the following signals: (1) Wind force and Ekman pump are very weak; (2) the cold  and high chlorophyll-a  tongue is shifted northward but not extended eastward; (3) for years when El Nino occurs, SST strongly increases and reaches a peak in May or early June of next year, during the declining phase of El Niño episode; (4) upwelling phenomenon typically occurs during August and not July. Using a reanalysis dataset derived from the HYCOM/NCODA system coupled with a local Finite Element Model (FEM) allow us to complete our knowledge about the abnormal oceanographic characteristics of deeper water layers after El Niño episodes. The analysis of spatial variations of oceanography fields derived from HYCOM/NCODA/FEM system along zonal and meridional sections and vertical profiles as well as the results obtained from water mass analysis allow us to identify in details the abnormal oceanic characteristics of deeper water layers during the declining  El Niño phase. Those are; (5) Sea water in both surface and deeper water layers were transported dominantly northward  but not eastward; (6) The thermo-halocline layer in South Vietnam upwelling center was deeper (about 90 -100m), compared with previous El Nino and normal years (50-60 m and 35-40 m, respectively); (7) Extreme global warming in recent years (2012-2016) pressed the thermo-halocline layer in upwelling center deeper (90-100 m) during summer. Under the influence of the ocean global warming, this process should progress continuously, the depth of thermo-halocline layer should become therefore deeper and deeper in next years.


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How to Cite

Son*, T. P. H., Chung, T. V., Huan, N. H., Tien, N. M., Tac, V. V., Khang, N. H. T., Hoi, N. T. T., Herrmann, M., & Siswanto, E. (2017). Abnormal features of oceanographic characteristics in upwelling Vietnam waters under impact of El Niño events. Vietnam Journal of Earth Sciences, 39(3), 225–239. https://doi.org/10.15625/0866-7187/39/3/10268




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